Buildings which are left unattended over extended periods of time, are often subject to burglary and theft, due to the ease with which they can be broken in to. The primary method of breaking and entering especially in cases where windows are not easily accessible, is through the building door.
Most building doors are provided with a standard lock arrangement in which a retractable latch is operated by a door knob rotatable in either direction for withdrawing the latch. For an experienced burglar, such a lock presents little or no obstacle to entering the building. The latch can easily be retracted or in some cases the exposed door hinges can be removed and the entire door is simply lifted out of the way.
According to the present invention, a lock is provided with first locking means comparable to the standard latch arrangement of a conventional lock. However, the present lock also includes second locking means and rotatable operating means for operating both the first and second locking means. When the operating means is rotated in one direction from a first position in which the first locking means is in a locking position and the second locking means is in an unlocking position, the first locking means is moved to the unlocking position without disturbing the second locking means. However, when the rotatable operating means is rotated in the opposite direction from the first position, the first locking means is maintained in its locking position and the second locking means is moved to a locking position.